Grab with adjustable guide mast



June 23, 1970 s. sERo'rA 3,516,183

GRAB WITH ADJUSTABLE GUIDE MAST Filed Jan. 29, 1968 2 sheets-sheet 1 Jud/11 MMLLMM ATTORNEYS J 23 1970 S. SEROTA 3, 6,

GRAB WITH ADJUSTABLE GUIDE MAST Filed Jan. 29, 1968 v 2 Sheets-Sheet 2 FIG.2.

INVENTOR /%Z//ZWZ [CQuQn 0 lfl w AT TO R N E YS United States Patent 3,516,183 GRA'B WITH ADJUSTABLE GUIDE MAST Stanley Serota, 111 Westminster Bridge Road, London, SE. 1, England Filed Jan. 29, 1968, Ser. No. 701,457 Int. Cl. E02f 3/96; E21b 15/00 US. Cl. 37-116 7 Claims ABSTRACT OF THE DISCLOSURE An excavator including a crane unit, a jib mounted on the crane unit, and a guide mast suspended from the upper end of the jib. The lower end of the guide mast is adjustably located by an arm extending from the crane unit. The guide mast includes a pair of rails, on which is mounted a carriage that is movable up and down the guide mast. A grab boom, which carries at its lower end a power operable grab, is pivotally suspended at its upper end on the carriage. The grab boom may be power driven downwardly to assist entry of the grab into the ground.

This invention relates to excavators which are particularly, but not exclusively, intended for use in excavating or digging trenches.

It has been known to excavate trenches in the ground with a grab carried on a crane or derrick, by raising the grab above the ground, dropping the grab in an open position onto the ground to penetrate into the ground, closing the grab, and then raising the grab to cut away a portion of the ground, the operation being repeated to form a trench. In building construction work, it is often necessary to dig trenches to a considerable depth as a preliminary to the construction, in the ground, of structural or non-structural Walls for foundations, tunnels, road underpasses, drainage cut off walls and the like.

Often when such trenches must extend to great depths and the walls of the trench are supported during excavation by the use of Bentanite/water mixtures in known manner. It has, however, proved difficult to control the vertical alignment of such trenches with the grab freely suspended from a derrick as done in past. Further the penetration of the grab into the ground has proved troublesome, particularly in hard clays or soft rocks, as the physical weight of the grab has been the sole means of causing the grab to penetrate the ground.

It is therefore an object of this invention to provide a mobile excavator which is capable of excavating such trenches accurately to considerable depths, and which is more effective, than excavators hitherto known, in breaking through hard ground.

Accordingly the present invention provides an excavator comprising a crane unit, a jib mounted on that crane unit, a guide mast suspended from said jib by one end and adjustably located relative to said crane unit at the other end, a grab boom mounted by one end for movement along said guide mast and suspended by a wire from said crane unit passing over said jib, a power operably grab mounted on the other end of said boom, and power means for driving said boom down said guide mast to force said grab into the ground.

In order to promote a fuller understanding of the invention one embodiment will now be described, by way of example only, with reference to the accompanying drawings in which:

FIG. 1 shows a schematic side view of an excavator; and

FIG. 2 shows a schematic front view of the excavator on an enlarged scale.

The excavator is shown in the drawing operating from 3,516,183 Patented June 23, 1970 ground level indicated at 1 to excavate an area which may be a trench, generally shown at 2.

The excavator comprises a power operated grab 3 comprising two jaws 4 and 5 which are each pivotally mounted on a grab body 6. The jaws 4 and 5 are operated by hydraulic rams 7 and 8, respectively, the hydraulic rams being pivotally mounted on the grab body 6 and piston rods being pivotally mounted on their respective grab jaws 4 and 5. The whole grab 3 is provided with a protective outer cover 54.

The grab 3 is rigidly attached to the lower end of a boom 9 which is suspended generally vertically in operation, the upper end of the boom 9 being pivotally mounted at a point 10 in a carriage 11. The means by which the boom 9 is pivotally mounted at the point 10 allows the boom 9 a limited universal movement relative to the carriage 11 so that it may swing freely from the carriage 11 by a small amount in any direction.

The carriage 11 is arranged to run vertically in and to be guided by a light generally vertical guide mast shown generally at 12. The carriage 11 is provided with suitable means such as slippers or rollers arranged to co-operate with guide rails 30 provided along the length of the guide mast 12.

The guide mast 12 is pivotally suspended from a lifting jib 13 of a mobile crane unit indicated at 14. The mobile crane unit 14 is of generally conventional design being carried on and transported by caterpillar tracks 15 and being capable of rotary or slewing action about the axis 16 relative to the tracks 15. The crane unit 14 also includes a prime mover, such as a diesel engine, to provide the necessary power for it to transport itself on the tracks 15 and to drive winches (not shown) within the body 17 of the crane unit and is also provided with a hydraulic power supply unit (not shown) for the operation of the grab 3, and other purposes to be described later, such supply unit being driven by the main diesel engine or by a separate engine.

The jib 13 may be raised or lowered by means of a cable 18 which is connected to and operated by a power driven winch (not shown) within the body 17. The boom 9 is suspended from and may be raised or lowered by a cable 19 which passes over suitably positioned pulleys on the jib 13 to a power operated winch (not shown) with in the body 17.

A guide bracket 20 is provided to locate the lower end of the guide mast 12 relative to the crane unit 14, the guide bracket 20 being supported from the body 17 of the crane unit by means of an arm 21. The arm 21 is braced so as to be rigidly attached to the body 17 by means of braces 22. The guide mast rails 30 have projecting portions 23 at their lower ends which are slidably fitted into universal mountings 57 carried on arms 31 provided on the guide bracket 20.

The guide bracket 20 is mounted on the arm 21 in such manner that it may be adjusted relative to the crane unit in all directions in a horizontal plane. In order that such adjustment of the guide bracket 20 may be achieved it is slidably mounted on a frame 40 so as to be movable towards or away from the crane unit 12 under the influence of a lead screw 50 which may be power driven by means of a hydraulic motor 51 or other rotary actu ator, or alternatively may be hand driven through suitable gearing. Thus the lovver end of the guide mast 12 can be adjusted towards or away from the crane unit 14 for vertical alignment. In order that the lower end of the guide mast may be adjusted sideways relative to the crane unit 14 for vertical alignment, the frame 40 is slidably mounted in a sideways direction on the arm 21 by means of bars 52 and is movably under the influence of a hydraulic piston and cylinder device 53.

Thus it can be seen that the grab 3 on its boom 9 may be positioned above a point to be excavated by lufling the jib 1 3 by means of the cable 18 and slewing the crane unit 14 about the axis 16 to bring the suspension point above that point, and the guide mast 12 may subsequently be brought into vertical alignment by adjustment of the guide bracket relative to the arm 21.

When the grab 3 is to be positioned above a point in the ground to be excavated, it is raised to an upper position by means of the cable 19. Once it has been so positioned as described above, the cable 19 is allowed to run out from its winch so that the grab 3 under its own weight penetrates the ground to a certain extent. In order to enhance the penetration of the grab 3 the carriage 11 is pulled down on the guide mast rails 30 by means of a cable which is attached to the top of the boom 9, and which passes around a pulley 26 which is rotatably mounted on the guide bracket 20, and then onto a power driven winch (not shown) within the body 17 of the crane unit 14. Thus it can be seen by operation of the cable 25 the carriage 11 is driven downwards under power, being of course guided by the rails 30, and consequently, by means of the boom 9, forces the grab 3 down to cause further penetration of the ground. Once the grab has penetrated to a sufiicient depth for its jaws 4 and 5 to be full, the jacks 7 and 8 are operated to close the jaws, the cable 25 is released, and the grab is then raised by the cable 19 taking with it the enclosed excavated material. The crane unit 14 may be slewed around the axis 16 so that the excavated material may be dumped to one side by opening the jaws 4 and 5.

In order to prevent the boom 9 and the grab 3 from swinging excessively from the carriage 11 while the crane unit 14 is being slewed around its axis 16 or transported on the tracks 15, a loose guide 27 is provided on the lower end of the guide mast 12 to limit the scope of swing allowed the boom 9. The loose guide 27 may take the form of a hoop attached to the guide mast 12 encircling the boom 9, or may simply be a loop of stel rope attached to the guide mast 12.

It will be appreciated that the arrangement described is suitable for a variety of excavating operations, and as excavation progresses, the whole equipment may be moved appropriately on the tracks 15 to excavate on elongated area or trench.

When it is desired to dig a trench with this equipment, in the arrangement shown in the figure, the grab 3 would be operated to excavate, removing its capacity of material successively, until the desired depth of trench is achieved at that one position, such depth being limited only by the length of the boom 9 and the scope of the movement of the carriage 11 allowed by the rails on the guide mast 12, and then the crane unit 14 is progressed, as seen in FIG. 1, on the tracks 15 whereupon excavation of the next section of the trench is carried out to progressively form a trench of a width corresponding to that of the grab. It will be appreciated that with such an arrangement the tracks 15 of the crane unit will progress along a line parallel to the trench being dug and lying to one side thereof.

An alternative arrangement for producing a trench with this equipment is with the crane unit 14 slewed around its axis 16 so that the tracks 15 are running in a direction to the left or right as shown in the FIG. 1. With this arrangement the mode of excavation is similar to that described above, with the exception that the crane unit 14 will progress along with its tracks 15 running one on either side of the trench being dug, and the grab would be turned through 90 with respect to the boom 9 and the jib 13.

The jib 13, the guide mast 12 and the grab boom 9 may preferably include removable sections indicated generally at so that the height of the excavation and the maximum depth of excavation may be adjusted.

1 Further the grab boom 9 may include a scale 56 where the depth of penetration may be indicated.

In order that hydraulic fluid may be supplied for the operation of the grab 3, flexible hydraulic pipes 60 are provided, hung by one end from the jib 13 and by the other end from the carriage 11.

Thus it can be seen that the invention provides an excavator in which the grab is driven into the ground under power thus enhancing the penetration achievable by a grab of a given Weight and consequently given increased excavating capacity with lighter and more economically constructed equipment.

Further it can be seen that the upper end of the grab boom is constituted to a vertical path as the grab is forced into the ground and with the result that the grab entry is controlled resulting in closer control of the inclination of the trench produced.

It can be seen that such equipment may be used for a variety of excavating operations including dredging, and the scope of the invention is not limited to the above described embodiment, but only by the scope of the following claims.

I claim:

1. An excavator comprising a crane unit, a jib mounted on said crane unit, a guide mast suspended from said jib at one end and adjustably located relative to said crane unit at its other end, at least two guide rails mounted on said guide mast, a carriage movably mounted on said rails, a grab boom pivotally mounted at one end on said carriage for movement along said guide mast, and a power operable grab mounted on the other end of said boom.

2. An excavator as claimed in claim 1 wherein said guide rails of said guide mast are provided with extensions at said other end of the guide mast, and a guide bracket is adjustably mounted on an arm extending from said crane unit, said guide bracket having universal mountings receiving said extensions of said guide rails.

3. An excavator as claimed in claim 2 wherein said guide bracket is mounted on a frame so as to be slidable towards and away from said crane unit under the influence of first power operated means, said frame being mounted on said arm so as to be slidable sideways relative to said crane unit under the influence of second power operated means.

4. An excavator as claimed in claim 3 wherein said first power operated means includes a lead screw connected to said frame for moving said bracket towards and away from said crane unit, said lead screw being adapted to be driven by a hydraulic motor.

5. An excavator as claimed in claim 3 wherein said second power operated means comprises a hydraulic piston and cylinder device connected to said frame unit, and is adapted to move said bracket sideways relative to said crane unit.

6. An excavator as claimed in claim l including power means for driving said grab boom down said guide mast to force said grab into the ground.

7. An excavator as claimed in claim 6 wherein said power means for driving said grab boom comprise a power winch in said crane unit and a wire rope extending from said power winch to an attachment point at said one end of said grab boom by way of a pulley rotatably mounted at said other end of the guide mast.

References Cited UNITED STATES PATENTS 2,292,867 8/1942 Charles 220 X 2,822,147 2/1958 Allard 175-220 X 2,594,720 4/1952 Beck 37--184 2,731,163 1/1956 Wills et al. 37-l86 2,889,642 6/1959 Stein 37-186 (Other references on following page) 5 References Cited Watson 173-147 .Hedin 214-658 Curtis 173-147 Spannhake et a1 254-172 5 Yost 37-184 Wailers 37-183 Witwer 173-151 6 ROBERT E. PULFREY, Primary Examiner E. H. EICKHOLT, Assistant Examiner US. Cl. X.R. 

